1. Field of the Invention
The present invention relates to an apparatus and method for the processing of wet material. In particular, to an apparatus that utilizes cyclonic forces and a heat processing to separate and size reduce wet material and for pathogen reduction.
2. Background
A wide range of commercial and municipal industrial operations produce wet materials as a byproduct of these various industrial processes. For example, in the United States municipal facilities that use biological processes to treat waste water solids create enormous quantities of biosolids. The Environmental Protection Agency (xe2x80x9cEPAxe2x80x9d) estimates that such facilities generated 6.9 million tons of biosolids in 1998, and the EPA predicts this output will continue to increase for the foreseeable future. Biosolids consist of nutrient rich organic matter produced from the stabilization of sewage sludge and residential septage and under the right conditions can be reclaimed or recycled for use as a land applied fertilizer. However, in its raw form biosolids are a pollutant subject to strict federal regulation at the hands of the EPA, and biosolids are similarly regulated by counterpart state and municipal authorities as well.
Considerable effort has been devoted to recycling or reclaiming biosolids for beneficial uses like for use as a land applicant fertilizer. The various treatment schemes include alkaline stabilization with such substances as lime, cement, or ash; anaerobic biological digestion in large closed tanks to allow decomposition through introduction of microorganisms; aerobic digestion in vessels that utilize aerobic bacteria to convert biosolids to CO2 and water; composting which regulates decomposition in a manner that elevates the temperature of the biosolids to a level that will destroy most pathogens; other processes include heat drying and pelletizing through the use of passive or active dryers, and dewatering. These efforts have met with some success but generally have been hindered by a public opposition based on concerns about pollution, odor, risk of disease, and other perceived nuisance issues, and by the strict regulatory frameworks that govern the use and recovery of biosolids. Again, the EPA estimates that in 1998 only 41% of biosolids were sufficiently reclaimed to allow for land application, another 19% were reclaimed for other beneficial uses; however, a full 37% of biosolids were incinerated or disposed of at landfills.
The concerns of the public with regard to the collection, reclamation, and subsequent use of biosolids are not totally unfounded. Untreated or minimally treated biosolids could carry pathogens, disease-causing organisms, which include certain bacteria, viruses, or parasites. Furthermore, biosolids are a vector attractant for such organisms as rodents and insects that can carry diseases in their own right, or become carriers of biosolid pathogens. There is concern about biosolid contamination of ground and surface water supplies. As a result, the use of biosolids is regulated to reduce these risks and set standards for the subsequent use of processed biosolids. The EPA framework for regulation generally classifies biosolids into two groups based on the level of potential risks to society.
Class A biosolids typically undergo advanced treatment to reduce pathogen levels to low levels. Normally, this is achieved through the previously discussed methods of heat drying, composting, or high-temperature aerobic digestion. Provided that the biosolids also meet the requirements for metal concentration and vector attraction reduction, Class A biosolids can be used freely and for the same purposes as any other fertilizer or soil amendment product.
Class B biosolids are treated to reduce pathogens to levels protective of human health and the environment, with limited access. Thus, the use of Class B biosolids require crop harvesting and site restriction, which minimize the potential for human and animal contact until natural attenuation of pathogens has occurred. Class B biosolids cannot be sold or given away for use on sites such as lawns and home gardens, but can be used in bulk on agricultural lands, reclamation sites, and other controlled sites provided that certain vector, pollutant, and management practice requirements are also met.
Clearly, it is highly desirable to process biosolids into a Class A product, however, the prior art methods of doing so leave much room for improvement in that these methods of treating biosolids involve large, expensive, fixed resources. The biosolid processing or treatment sites are usually not located at a majority of the generation sites thereby requiring transportation of the biosolids. Or, a biosolid treatment facility must be constructed adjacent to each collection facility. In addition, many of these processes are slow thereby limiting the efficiency of conversion of biosolids, or the processes are not cost effect given the commercial value of Class A biosolids. As a result there is much room for improvement in the recover of biosolids for beneficial uses.
Furthermore, the problems associated with biosolids are not unique. Many other types of wet material that result from industrial processing also fall into the category of products that may breakdown into products capable of beneficial use subject to the restriction of commercially viable methods of processing the wet material. These materials include, without limitation, calcium carbonate, calcium sulfate, mycelium, coal fines, lime sludge, paper sludge, compost, saw dust, animal waste, including manure, or any other material in need of drying and/or reduction.
Thus, a need exists for an improved apparatus and method of processing these types of wet materials.
An object of the present invention comprises providing an improved apparatus and method for processing wet material.
These and other objects of the present invention will become apparent to those skilled in the art upon reference to the following specification, drawings, and claims.
The present invention intends to overcome the difficulties encountered heretofore. To that end, a waste treatment apparatus for the treatment and processing of wet material is provided. The apparatus comprises an inlet hopper adapted for receipt of the wet material. A pre-conditioning unit is provided having an input and an output end wherein the wet material is received from the inlet hopper at the input end and is conveyed to the output end wherein the wet material is processed to reduce moisture and pathogen content. A blower is provided for providing a forced air stream to direct the flow of the wet material and for directing the flow from the output end of the pre-conditioning unit. A pre-separation cyclone is provided and is operatively positioned for receiving the wet material from the output end of the pre-conditioning unit via the air stream powered by the blower, wherein the wet material is processed under the influence of cyclonic forces that further reduce the moisture content, pathogen content, and reduce the particle size of the wet material. A separation cyclone is provided and is operatively positioned for receiving the wet material from the pre-separation cyclone via the air stream powered by the blower, wherein the wet material is processed under the influence of cyclonic forces that separate the wet material into a substantially dry portion that exits from a lower portion of the separation cyclone and a substantially liquid or vapor portion that exits from an upper portion of the separation cyclone. A wet scrubber is provided and is operatively positioned for receiving the substantially liquid portion of the wet material.